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The present invention relates generally to surgical tools and, more particularly, to various wrist mechanisms in surgical tools for performing robotic surgery.
Robotic surgery has developed to improve and expand the use of minimally invasive surgical (MIS) techniques in the treatment of patients. Minimally invasive techniques are aimed at reducing the amount of extraneous tissue that is damaged during diagnostic or surgical procedures, thereby reducing patient recovery time, discomfort, and deleterious side effects. The average length of a hospital stay for a standard surgery may also be shortened significantly using MIS techniques. Thus, an increased adoption of minimally invasive techniques could save millions of hospital days and millions of dollars annually in hospital residency costs alone. Patient recovery times, patient discomfort, surgical side effects and time away from work may also be reduced with minimally invasive surgery.
The most common form of minimally invasive surgery may be endoscopy. And, probably the most common form of endoscopy is laparoscopy, which is minimally invasive inspection and surgery inside the abdominal cavity. In standard laparoscopic surgery, a patient""s abdomen is insufflated with gas, and cannula sleeves are passed through small (approximately xc2xd inch) incisions to provide entry ports for laparoscopic surgical instruments. The laparoscopic surgical instruments generally include a laparoscope (for viewing the surgical field) and working tools. The working tools are similar to those used in conventional (open) surgery, except that the working end or end effector of each tool is separated from its handle by an extension tube. As used herein, the term xe2x80x9cend effectorxe2x80x9d means the actual working part of the surgical instrument and can include clamps, graspers, scissors, staplers, and needle holders, for example. To perform surgical procedures, the surgeon passes these working tools or instruments through the cannula sleeves to an internal surgical site and manipulates them from outside the abdomen. The surgeon monitors the procedure by means of a monitor that displays an image of the surgical site taken from the laparoscope. Similar endoscopic techniques are employed in, e.g., arthroscopy, retroperitoneoscopy, pelviscopy, nephroscopy, cystoscopy, cisternoscopy, sinoscopy, hysteroscopy, urethroscopy and the like.
There are many disadvantages relating to current MIS technology. For example, existing MIS instruments deny the surgeon the flexibility of tool placement found in open surgery. Most current laparoscopic tools have rigid shafts, so that it can be difficult to approach the worksite through the small incision. Additionally, the length and construction of many endoscopic instruments reduces the surgeon""s ability to feel forces exerted by tissues and organs on the end effector of the associated tool. The lack of dexterity and sensitivity of endoscopic tools is a major impediment to the expansion of minimally invasive surgery.
Minimally invasive telesurgical robotic systems are being developed to increase a surgeon""s dexterity when working within an internal surgical site, as well as to allow a surgeon to operate on a patient from a remote location. In a telesurgery system, the surgeon is often provided with an image of the surgical site at a computer workstation. While viewing a three-dimensional image of the surgical site on a suitable viewer or display, the surgeon performs the surgical procedures on the patient by manipulating master input or control devices of the workstation. The master controls the motion of a servomechanically operated surgical instrument. During the surgical procedure, the telesurgical system can provide mechanical actuation and control of a variety of surgical instruments or tools having end effectors such as, e.g., tissue graspers, needle drivers, or the like, that perform various functions for the surgeon, e.g., holding or driving a needle, grasping a blood vessel, or dissecting tissue, or the like, in response to manipulation of the master control devices.
Manipulation and control of these end effectors is a critical aspect of robotic surgical systems. For these reasons, it is desirable to provide surgical tools which include mechanisms to provide three degrees of rotational movement of an end effector around three perpendicular axes to mimic the natural action of a surgeon""s wrist. Such mechanisms should be appropriately sized for use in a minimally invasive procedure and relatively simple in design to reduce possible points of failure. In addition, such mechanisms should provide adequate degree of rotation to allow the end effector to be manipulated in a wide variety of positions. At least some of these objectives will be met by the inventions described hereinafter.
The present invention provides a robotic surgical tool for use in a robotic surgical system to perform a surgical operation. Robotic surgical systems perform surgical operations with tools which are robotically operated by a surgeon. Such systems generally include master controllers and a robotic arm slave cart. The robotic arm slave cart is positioned adjacent to the patient""s body and moves the tools to perform the surgery. The tools have shafts which extend into an internal surgical site within the patient body via minimally invasive access openings. The robotic arm slave cart is connected with master controllers which are grasped by the surgeon and manipulated in space while the surgeon views the procedure on a stereo display. The master controllers are manual input devices which preferably move with six degrees of freedom, and which often further have an actuatable handle for actuating the tools (for example, for closing grasping saws, applying an electrical potential to an electrode, or the like). Robotic surgery systems and methods are further described in co-pending U.S. patent application Ser. No. 08/975,617, filed Nov. 21, 1997, the full disclosure of which is incorporated herein by reference.
As described, robotic surgical tools comprise an elongated shaft having a surgical end effector disposed near the distal end of the shaft. As used herein, the terms xe2x80x9csurgical instrumentxe2x80x9d, xe2x80x9cinstrumentxe2x80x9d, xe2x80x9csurgical toolxe2x80x9d, or xe2x80x9ctoolxe2x80x9d refer to a member having a working end which carries one or more end effectors to be introduced into a surgical site in a cavity of a patient, and is actuatable from outside the cavity to manipulate the end effector(s) for effecting a desired treatment or medical function of a target tissue in the surgical site. The instrument or tool typically includes a shaft carrying the end effector(s) at a distal end, and is preferably servomechanically actuated by a telesurgical system for performing functions such as holding or driving a needle, grasping a blood vessel, and dissecting tissue. In addition, as used herein, xe2x80x9cend effectorxe2x80x9d refers to the actual working part that is manipulable for effecting a predetermined treatment of a target tissue. For instance, some end effectors have a single working member such as a scalpel, a blade, or an electrode. Other end effectors have a pair or plurality of working members such as forceps, graspers, scissors, or clip appliers, for example.
In a first aspect of the present invention, the robotic surgical tool includes a wrist mechanism disposed near the distal end of the shaft which connects with the end effector. The wrist mechanism includes a distal member, configured to support the end effector, and a plurality of rods extending generally along an axial direction within the shaft and movable generally along this axial direction to adjust the orientation of the distal member with respect to the axial direction or shaft. The distal member may have any form suitable for supporting an end effector. In most embodiments, the distal member has the form of a clevis. In any case, the distal member has a base to which the rods are rotatably connected.
Advancement or retraction of a first rod generally along the axial direction tips the base through a first angle so that the distal member faces a first articulated direction. The first angle may be any angle in the range of 0-90 degrees and oriented so that the first articulated direction is any direction that is not parallel to the axial direction. This would allow the distal member to direct an end effector in any direction in relation to the shaft of the surgical tool. In most embodiments, the first angle is greater than approximately 30 degrees. In some embodiments, the first angle is greater than approximately 60 degrees and in other embodiments the first angle is greater than approximately 70 degrees. This first angle may represent the pitch or the yaw of the wrist mechanism.
In some embodiments, advancement or retraction of a second rod generally along the axial direction tips the base through a second angle so that the distal member faces a second articulated direction. The second angle may also be any angle in the range of 0-90 degrees and oriented so that the second articulated direction is any direction that is not parallel to the axial direction. The addition of a second angle would allow the distal member to direct an end effector in essentially a compound angle or in a second articulated direction in relation to the shaft of the surgical tool. In most embodiments, the second angle is greater than approximately 30 degrees. In some embodiments, the second angle is greater than approximately 60 degrees and in other embodiments the second angle is greater than approximately 70 degrees. If the first angle represents the pitch of the wrist mechanism, the second angle may represent the yaw of the wrist mechanism and vice versa.
The plurality of rods may comprise two, three, four or more rods. In preferred embodiments, three or four rods are used to provide both pitch and yaw angulation. When four rods are used, the first and second rods are positioned adjacent to each other and the remaining two rods are located in positions diametrically opposite to the first and second rods. The four rods are generally arranged symmetrically around a central axis of the shaft or the axial direction. When the first rod is advanced, the diametrically opposite rod is simultaneously retracted. Likewise, when the first rod is retracted, the diametrically opposite rod is simultaneously advanced. This is similarly the case with the second rod and its diametrically opposite rod. Thus, the rods actuate in pairs. Such actuation will be further described in a later section.
To maintain desired positioning of the rods, some embodiments include a guide tube having a plurality of guide slots. Each guide slot is shaped for receiving and guiding one of the plurality of rods substantially along the axial direction. In some embodiments, the rods are shaped so as to have a rectangular cross-section. In these instances, the corresponding guide slots also rectangular in shape to receive and maintain proper orientation of the rods.
In a second aspect of the present invention, the robotic surgical tool includes a tool base disposed near the proximal end of the shaft. The tool base includes mechanisms for actuating the wrist mechanism and often mechanisms for actuating the end effector. Mechanisms for actuating the wrist mechanism includes mechanisms for advancing or retracting the first rod. In some embodiments, such mechanisms comprises a first rotational actuation member to which the first rod is attached so that rotation of the first rotational actuation member advances or retracts the first rod. Typically, another rod is attached to the first rotational actuation member in a position diametrically opposite to the first rod so that rotation of the first rotational actuation member simultaneously advances the first rod and retracts the diametrically opposite rod. In some embodiments, the tool base further comprises a second rotational actuation member to which the second rod is attached so that rotation of the second rotational actuation member advances or retracts the second rod substantially along the axial direction. Again, another rod is often attached to the second rotational actuation member in a position diametrically opposite to the second rod so that rotation of the second rotational actuation member simultaneously advances the second rod and retracts the diametrically opposite rod. Thus, by rotating the first and second rotational actuation members, the distal member is tipped through two angles, or a compound angle, so that the distal member faces any desired direction. This allows refined control of the end effector throughout three dimensions.
The robotic surgical tool of the present invention may also include provisions for roll movement. Roll movement is achieved by rotating the shaft around its central axis. Since the shaft is connected to a guide tube through which the plurality of rods pass, rotation of the shaft rotates guide tube which in turn rotates the rods around the central axis which is parallel to the axial direction. To actuate such roll, the above described tool base comprises a roll pulley which rotates the shaft. Since the rods extend through the roll pulley and attach to the rotational actuation members, such rotation is possible by flexing of the rods. Due to the length, thickness and flexibility of the rods, 360 degree rotation is possible. Thus, pitch, yaw and roll movement can be individually actuated by the tool base, particularly by manipulation of the rotational actuation members and roll pulley.
Although actuation of the wrist mechanism is achieved by manipulation of the rods, it is the connection of the rods to the base which allows tipping and manipulation of the distal member to face a desired direction. Such connection is achieved with the use of a plurality of linkages, each linkage connecting one of the plurality of rods with the base. In some embodiments, the linkages comprise orthogonal linkage assemblies. Each orthogonal linkage assembly rotatably connects one of the plurality of rods with the base to allow the base to be rotated in at least two directions with respect to the axial direction. In some embodiments, each orthogonal linkage assembly comprises an orthogonal linkage having a first link portion which is rotatably connectable with the one of the plurality of rods and a second link portion which is rotatably connectable with the base and wherein the first link portion and the second link portion lie in orthogonal planes. In other embodiments, each orthogonal linkage assembly comprises a linkage fastener having a link base portion which is rotatably connectable with one of the plurality of rods and a cylindrical fastening end portion which is rotatably connectable with the base. The different orthogonal linkage assemblies allow the base to be rotated to different degrees of angularity relative to the axial direction.
Such rotation is assisted by flexibility of the rods. Generally, each rod is flexible in at least one direction. For example, when each rod has a rectangular cross-section, having a wide side and a narrow side, the rod may be flexible along the wide side yet rigid along the narrow side. When the rods are arranged so that the wide sides are parallel to the perimeter of the shaft, flexibility along the wide sides allows each rod to bend slightly inward, toward the center of the shaft or the longitudinal axis. This allows greater rotation of the distal member and flexibility in design parameters.
In a third aspect of the present invention, methods of actuating the robotic surgical tool are provided. In some embodiments, methods include providing a robotic surgical tool comprising a wrist mechanism, which includes a distal member coupleable with a surgical end effector and having a base and a plurality of rods rotatably connected to the base and extending along an axial direction, and actuating the wrist by manipulating a first rod of the plurality of rods to tip the base through a first angle so that the distal member faces a first articulated direction. Manipulating typically comprises advancing or retracting the first rod. As previously mentioned, advancing or retracting may comprise rotating a first rotational actuation member to which the first rod is attached. Likewise, actuating the wrist may further comprises manipulating a second rod of the plurality of rods to tip the base through a second angle so that the distal member faces a second articulated direction. Again, advancing or retracting may comprise rotating a second rotational actuation member to which the second rod is attached.
In some embodiments, methods further comprise actuating the wrist by rotating the plurality of rods around a longitudinal axis parallel to the axial direction to rotate the base. In some embodiments, rotating the plurality of rods comprises rotating a roll pulley through which the plurality of rods extend. And, lastly, methods may further comprise coupling the end effector to the base and actuating the end effector.
Other objects and advantages of the present invention will become apparent from the detailed description to follow, together with the accompanying drawings.